The present invention relates to a method for writing and reading information on to and out of a storage medium, and more particularly to a method for writing and reading information suitable for controlling a read signal, an apparatus for writing and reading information using that method and a storage medium suitable for the use therefore.
For example, in JP-A-58-146039, an optical head for confirming that information has been written by reading the stored information immediately after the information is written on a storage medium for the purpose of detecting a defect on the storage medium in its early stages is disclosed. The structure thereof is shown in FIG. 6. The optical head of the apparatus shown in FIG. 6 includes a light source 60 for writing and a light source 68 for reading to confirm the writing. When information is written, a luminous flux 74 from the light source 60 for writing forms a writing spot with an objective lens 63, which is irradiated on to a medium 64. A luminous flux 75 from the light source 68 also forms a spot for confirmation with the objective lens 63, which is irradiated onto the medium 64. The reading spot for confirmation is positioned in the rear of the writing spot with respect to an onward direction. Namely, it is arranged for the purpose of confirming the information written by the writing spot by reading reflected light from the reading spot for confirmation to a signal detector 73 and reading the information.
The above-described prior art discloses a structure of a writing-reading head, however, no disclosure has been made on the structure and the method for processing signals for converting a signal obtained by the signal detector 73 into information and positional dislocation of the light spot for writing and reading.